Hydrophobe-substituted bPEI derivatives: boosting transfection on primary vascular cells

Gene therapy targeted to vascular cells represents a promising approach for prevention and treatment of pathological conditions such as intimal hyperplasia, in-stent and post-angioplasty restenosis. In this context, polymeric non-viral gene delivery systems are a safe alternative to viral vectors but a further improvement in efficiency and cytocompatibility is needed to improve their clinical success. Herein, a library of 24 branched polyethylenimine (bPEI) derivatives modified with hydrophobic moieties was synthesised, characterised and tested in vitro on primary vascular cells, aiming to identify delivery agents with superior transfection efficiency and low cytotoxicity. Low molecular weight PEIs (0.6, 1.2 and 2 kDa) were grafted with long (C18) and short (C3) aliphatic chains, featuring different unsaturation degrees and degrees of substitution. 0.6 kDa bPEI-based derivatives were generally ineffective in transfection on vascular smooth muscle cells (VSMCs), while among the other derivatives some promising vectors were identified. Forcing polyplexes on the cell surface by means of centrifugation invariably boosted transfection levels but increased cytotoxicity as well. Of note, a propionyl-substituted derivative (PEI2-PrA1, C3: 0) was the most effective on both VSMCs and endothelial cells (ECs), with higher and more sustained gene expression in combination with markedly lower cytotoxicity with respect to the gold standard 25 kDa bPEI. In addition, a linoleoyl-substituted derivative (PEI1.2-LA6, C18:2) owing to its high efficiency in VSMCs and relative inefficacy in ECs, combined with tolerable cytotoxicity was proposed as a vector for specific VSMCs targeting.